1. Field of the Invention
The present invention relates to a photosensitive material printing apparatus in which images recorded on an original film are printed onto a photosensitive material, and especially to a photosensitive material printing apparatus in which the original film is maintained at a predetermined position with respect to the photosensitive material so as to print the images on the original film at a predetermined position of the photosensitive material.
2. Description of the Related Art
Images recorded on an original film (e.g., a negative film) are printed by a photosensitive material printing apparatus (hereinafter referred to as "plate material printing apparatus") onto a photosensitive material (hereinafter referred to as "PS plate"). Examples of photosensitive material include a lithographic printing plate, which is used at a rotary press or the like used in printing newspapers, and a color photograph photosensitive material, which is used in producing color proofs, and the like.
A surface plate is disposed at a printing portion of the plate material printing apparatus. The PS plate, which is supplied to the printing apparatus by a PS plate supplying apparatus, is loaded at a predetermined position on the surface plate, At this time, the negative film is loaded while being registered to the predetermined position of the PS plate. As an example of this registration of the PS plate, convex portions, e.g., pins or the like, are provided at the surface plate or the like. Registration of the negative film is effected by the insertion of the convex portions into holes formed in advance in the negative film.
Deviation of printing position of an image on the PS plate for each printing apparatus from a standard printing position of the image on the PS plate is caused by either the displacement of the positions of the punch holes with respect to the image area on the original film (hereinafter referred to as "negative film") among printing apparatuses, or the placement of the positions of the positioning pins for the PS plate at the printing portion among printing apparatuses. The deviation is a drawback especially in color printing since the deviation becomes out of registration in colors.
Namely, extreme precision is required in order to accurately print the images at the predetermined positions on the PS plate. After the negative film is loaded onto the PS plate, it is necessary to finely adjust the position of the negative film in accordance with the deviation of each printing apparatus. Especially in color printing in which the images of negative films are color separated images, e.g., four colors of yellow, magenta, cyan, and black, the color separated images of the four colors are printed separately for each color image onto the PS plate. However, because of the deviation of the printing position of the images among printing apparatus, out of registration in color occurs when printing is effected at separate printing apparatuses.
Namely, when images of a plurality of negative films, which are separated for each color, are printed in parallel by using a plurality of plate material printing apparatuses, the printing of the images of the negative films onto the PS plate can be carried out quickly. In this case, registration of the negative films at each of the plate material printing apparatuses is extremely difficult due to the deviation of the printing position of each printing apparatus.
Further, when the above-mentioned punch holes of the negative film are formed as references for the edges of the negative film, there is often displacement of the image area with respect to the edges. Moreover, displacement arises due to differences in the positions of the punchers among printing apparatuses, which is a factor in out of registration in color especially in color printing.
The space between images when two or more images are printed onto one PS plate, i.e., the photocomposition pitch, differs for each user. Ordinarily, when the plate material printing apparatus is installed, the photocomposition pitch is adjusted.
There are differences, to a certain degree, in the accuracy of positioning of the PS plate in the printing portions of plate material printing apparatus. There are also differences in the position of punch holes formed in the negative film for each printing apparatus. Therefore, even if registration at the printing portion is carried out for each plate material printing apparatus, deviation in the position of an image printed on the PS plate from the standard position of the image on the PS plate arises. This deviation results in out of registration in the finished color print. In order to prevent out of registration of color images and the like, it is necessary to print the images, separated into four colors from one color image, onto the PS plate by the use of a single plate material printing apparatus. However, when this type of method is used for printing, printing work becomes less efficient,
Further, the plate material printing apparatus is generally not equipped with a special function for regulating the photocomposition pitch, and adjustment of the photocomposition pitch is not easily carried out.